class Battery:
    def __init__(self, battery_size=75):
         """初始化电瓶的属性。"""
         self.battery_size = battery_size
         
    def describe_battery(self):
         """打印一条描述电瓶容量的消息。"""
         print(f"This car has a {self.battery_size}-kWh battery.")
 
    def get_range(self):
         """打印一条消息，指出电瓶的续航里程。"""
         if self.battery_size == 75:
             range = 260
         elif self.battery_size == 100:
             range = 315
         else:
              range = 200 
         print(f"This car can go about {range} miles on a full charge.")

    def upgrade_battery(self):
        if self.battery_size != 85:
            self.battery_size = 85
        
